Turbine oil



Patented June 13, 1944 TURBINE OIL Daniel B. Luten, Jr., Berkeley,Calil'., assignor to Shell Development Company, San Francisco, Calii., acorporation of Delaware No Drawing. Application June 8, 1942, Serial No.446,291

' Claims.

This invention relates to the production of mineral oil compositionshaving properties which render them especially suitable for use aslubricants for turbines and as dielectrics for electrical equipment suchas transformers. It also deals with lubricating oils containing smallamounts of an addition agent which renders the oil highly resistant tooxidation and gum or slud e formation. More particularly, it deals withthe use of 2,4-dimethyl-6-tertiary octyl phenol for stabilizing turbineoils against oxidation and gum formation.

In the past, it has been recommended to add various anti-oxidants or guminhibitors to mineral'hydrocarbon oils to improve their oxidationstability. Among the suggested active inhibitors are the xylenols andthe trialkylated phenols. Of the latter, one having two methyl and onetertiary butyl group in the 2,4, and 6 positions, respectively, isparticularly effective.

Now I have discovered that 2,4-dimethyl-6- tertiary octyl phenolpossesses outstanding characteristics which distinguish this compoundfrom related tri-alkylated phenols for use in the particular mineral oilblends herein contemplated. These outstanding characteristics areimproved oxidation stability and reduced tendency to disperse iron rustin the compounded oil.

Good turbine oils must show their superior qualities in commercial use.In the lubrication of turbines, oil is constantly circulated from astorage system connected with the turbine to various parts to belubricated and back to storage. The oil is used over a long period oftime, during which time it comes in contact with the atmosphere as wellas with water. This contact leads to deterioration of the oil in thatthe conditions of use are conducive to oxidation and oil so oxidizedtends to emulsify with the water slowly accumulated in the circulatorysystem. Moreover, the practically unavoidable presence of waterfrequently causes rusting, particularly in the governor mechanism.Further, metallic iron and/or copper, which is always used in theconstruction of-turbine oiling systems, has a catalytic efiect on oiloxidation. A good turbine oil must therefore be highly resistant tooxidation in the presence of iron and copper, must not tend to dispersemetallic oxidation catalysts throughout the oil and must maintain areasonably high interfacial tension against water during use.

Turbine oils having the above properties can be produced from wellrefined lubricating oils of the proper viscosity range, which may beabout these lubricating oils about .01% to 1% of 2,4-dimethyl-S-tertiary octyl phenol.

The phenols which may be alkylated to form the useful tertiary octylantioxidant are either (1) pure 2,4-dimethyl phenol, or (2) a narrowboilin liquid phenol fraction having an A. S. T. M. 5% boiling point of206-211 (2., a 50% boiling point of 210-212 C. and a 95% boiling pointof 211-216 C. Preferably the 5% boiling point is not lower than 209C.and the 95% point not above 213 C. Such fraction normally contains about60% of 2,4-dimethyl phenol, the most important of the remaining phenolsbeing about 25% 2,5-dimethyl phenol.

Alkylation may be carried out by using as alkylating compound tertiarybase octylene such as di-isobutylene or so-called hot acid octylenes; ortertiary octyl chloride, or the corresponding alcohol, or di-tertiaryoctyl ether.

Catalysts or condensing agents useful in alkyating the phenols are theinorganic poly-oxy acids such as sulfuric acid, sulfonic acids,phosphoric acid, P205, etc.; Friedel-Craft catalysts such as aluminumchloride, zinc chloride, acid zinc sulfate, tin tetrachloride, ferricchloride, boron trichloride, boron fluoride; complex compounds ofFriedel-Crafts catalysts such as halides of Al, B, Fe, Sn, Sb and W,with inactive halide salts as NaCl, HgClz, AgCl, etc., or dissolved inorganic liquids such as nitrobenzene, acetone, acetophenone, benzoylchloride, di-ethyl sulfone,

ethyl phenyl sulfone, diphenyl sulfone, di-iso- -750 Say. Univ. Sec. atF. by adding to 65 propyl sulfate, ethyl benzol sulfonic acid ester,etc. acidic clays, silica gel, etc., and combinations of the above.Those familiar with the art know the proper catalysts to use with eachof the alkylating compounds mentioned above.

If desired, the reaction may be carried out in dilution of inertsolvents for the alkyl phenols such as carbon dlsulfide, nitrobenzene,parafllns free of reactive tertiary atoms, etc.-

Temperatures suitable for our process may vary with the catalyst butusually are between about 0 and 100 C. and the quantities of catalystsmay vary from very small amounts to those equalling or slightlyexceeding the amount of alkyl phenols present.

The following example illustrates one method of preparation of the2,4-dimethyl-6-tertiary octyl phenol: Starting material was xylenolfraction boiling at about 211 C. and containing 82.5% 2,4-dimethylphenol and 17.5% 2,5-dimethyl phenol, the latter being relativelyunreactive under the conditions of this reaction. To the xylenolfraction was added tertiary octyl chloride. ferric chloride and carbondisuliide. The mixture was refluxed for 8 hours. Carbon disulflde wasremoved under vacuum. The high boiling residue dissolved in benzene andthe solution was washed with water to remove ferric chloride. Thebenzene was distilled oil! under vacuum and thereafter a high boilingdistillate was taken overhead which was reiractionated at atmosphericpressure to distill unreacted 2,5- dimethyl phenol and to recover aproduct consisting essentially of 2,4-dimethyl-6-tertiary octyl phenol.

The amounts of inhibitor required to stabilize turbine oil variessomewhat with conditions and the secondary additives in the oil. Whenused alone, 2,4-dimethyl'-8-tertiary octyl phenol is useful up to about2%, although it rarely needs to exceed about .5% and generally may bebetween .05% to 3%.

2,4-dimethyl-6-tertiary octyl phenol may be used in combination withother secondary additivessuch as corrosion inhibitors, e. g. allwlsuccinic acids, aromatic imino alpha di-carboxylic acids, etc., E.'P.compounds,- blooming agents, etc.

The value of the 2,4-dimethyl-6-tertiary octyl phenol as a stabilizerior turbine oil is illustrated below:

A well-refined turbine oil oi. 150 S. S. U. viscosity at 100 F. treefrom added oxidation inhibitors was divided into three portions. To-oneportion was added 2% by weight of 2,4-dimethyl- I 'B-tertiary butylphenol. To another portion was [the top of the 3 oil layer. oxidationwere set up in a water bath to maintain the temperature of the oil at(2.11. Omen was then bubbled through each tube at the rate of 3 litersper hour. The passage or oxygen was maintained until the oil in eachtube darkened and its neutralization number had reached a value of 5. Vi t V Results were as iollowsz I claim as my invention:

1. A highly refined mineral lubricating oil containing less than 2% oi2,4-dimethyl-6-tertiary octyl phenol. 2. A mineral oil compositioncomprising turbine oil normally susceptible to oxidation underconditions encountered in use and a small amount of2,4-dimethyl-6-tertiary octyl phenol suillcient to retard oxidation.

3. Turbine 011 comprising predominantly a refined mineral lubricatingoil having a viscosity at F. or 75 to 750 Bay. Univ. Seconds, andcontaining dissolved 415% to 2% of 2,4-dimethyld-tertiary octyl phenol.

.4. Turbine oil comprising predominantly a refined mineral lubricatingoil having a viscosity at 100 I". of 7,5 to 750 Bay. Univ. Seconds, andcontaining dissolved .05% to 3% of 2,4-dlmethyld-tertiary'octyl phenol.

5. A refined hydrocarbon oil subject to oxidation, containing as anactive anti-oxidant 2,4- dimethyl-B-tertiary octyl phenol.

DANIEL B. LUTEN, Ja.

